1. Field of the Invention
The invention relates to fastening buckles using a manipulation lever and provided to bring two sides closer together. More particularly, the invention relates to buckles for fastening sports boots for closing and/or tightening portions of a boot around the foot or lower leg of a wearer, as well as to a boot having such buckle(s).
2. Description of Background and Other Information
Buckles of the aforementioned type are especially used for fastening ski boots. However, they can be used for any other items, such as skate boots, boot bindings for a gliding board, luggage closures, etc.
To fasten sports boots having a rigid shell, such as an alpine ski boot, it is known to use metallic buckles, which are used to bring two sides of the shell closer together and to keep them tightened. Typically, buckles of this type are fixed on one of the two sides of the shell. An attachment rack equipped with a plurality of teeth is attached to the other side of the shell. To tighten, the latch of the buckle is engaged with one of the teeth of the rack; a device in the buckle then enables the latch to be displaced by an amplitude “d”, referred to as the tightening amplitude. To displace the latch along the tightening amplitude, it is commonly known to use so-called knuckle-joint, or over-center, mechanisms.
In a knuckle-joint mechanism, the buckle includes a cap fixed to the first side, as well as a lever pivotally mounted about a first axis relative to the cap. The buckle also includes a tie rod, or linking rod, that is pivotally mounted on the lever about a second axis. The tie rod is affixed to the latch, the connection between the tie rod and the latch being capable of being articulated about a third axis. In order for the buckle to work, the first axis and the second axis must not be coaxial. In practice, the distance “e” separating the first axis from the second axis determines the maximum tightening amplitude. Indeed, the maximum tightening amplitude “d” is equal to twice the distance “e”, which separates the first axis from the second axis. Furthermore, in order for the buckle to function according to the knuckle-joint principle, the position of the second axis must be beneath a plane of equilibrium when the buckle is closed. The plane of equilibrium is the plane that contains the first axis, and which passes through the connection point between the tie rod and the latch.
To increase the tightening amplitude, the distance separating the first axis from the second axis can be increased. This solution has a number of drawbacks.
For example, when the distance separating the first axis from the second axis is increased, the torque that must be applied by the lever in order to tighten is thereby increased. However, such buckles are adapted to be manipulated by hand, and too substantial a torque for actuating the buckle is problematic for users who do not have adequate physical strength.
To solve this problem, prior art systems have been proposed to assist in tightening. The document DE 202 11 689 describes such a device, which is a lever extender. It includes a hollow portion adapted to receive the free end of the lever. The user therefore slips this tool on the lever in order to lengthen the lever and, therefore, to obtain a more substantial lever arm. This provides the user with the ability to apply a greater tightening fore.
This solution is not satisfactory as it requires using an additional tool that the user must carry around. Furthermore, the tool must be dedicated to the buckles of the boot, as there is no guarantee that such an adapter would function on all types of buckles, each buckle having a particular lever shape.
U.S. Pat. No. 6,145,168 describes another solution to the aforementioned problem. The buckle described in this document has an additional lever that is pivotally mounted on the main lever and makes it possible to extend the main lever. This solution is no more satisfactory then the previously mentioned solution insofar as it requires learning how the lever functions. Indeed, the functioning of such a lever is slightly different from the functioning of a conventional lever. The user must first pivot the additional lever, such pivoting movement being done in a direction that is opposite the pivoting direction of the main lever.